Thirty-eight percent of colorectal cancer cases linked to nutrition, as research estimates rate of diet-related preventable cancer

23 May 2019 --- A modeling study published in JNCI Cancer Spectrum estimates the number, proportion and type of specific cancers associated with the consumption of certain diets and sugar-sweetened beverages among US adults. One of the main findings is that an estimated 38.3 percent of colorectal cancer cases in 2015 were linked to sub-optimal diets. The analysis is cited as one of the few to focus on the modifiable risk factors for cancer connected to food intake in the US. Authors also recommend this should be in greater focus as a preventative measure against the disease.

Findings of the research estimates that diet-related factors may account for 80,110 of the new invasive cancer cases reported in 2015, or 5.2 percent of that year's total among US adults. This is comparable to the cancer burden associated with alcohol, which has a four to six percent prevalence. Excessive body weight, meanwhile, is associated with 7 to 8 percent of the cancer burden, and physical inactivity is associated with two to three percent.

“Our findings underscore the opportunity to reduce cancer burden and disparities in the US by improving food intake,” says first and corresponding author Fang Fang Zhang, a Cancer and Nutrition Researcher at the Friedman School of Nutrition Science and Policy at Tufts University.

To estimate the cancer burden associated with sub-optimal diet, the researchers utilized the risk estimates of diet and cancer relations based on a meta-analyses of prospective cohort studies, with limited evidence of bias from confounding. In this research, studies were primarily sourced from the World Cancer Research Fund International (WCRF) and the American Institute for Cancer Research (AICR) Third Expert Report.

The AICR Third Expert Report indicates that there is convincing or probable evidence for diets yielding low whole grains, low dairy, high processed meat and high red meat consumption on colorectal cancer risk; low fruit and vegetable consumption on risk of cancer of the mouth, pharynx, and larynx; and high processed meat consumption on stomach cancer risk. Researchers of this study also examined sugar-sweetened beverages, due to their known associations with obesity and 13 types of cancer.

Findings of the meta-analysis concluded:

• Colorectal cancer had the highest proportion of diet-related cases, with 38.3 percent of all cases in 2015 associated with suboptimal diets. This was followed by cancer of the mouth, pharynx and larynx, which the study linked to diet in 25.9 percent of all cases;
• Low whole grain intake was associated with the largest number and proportion of new cancer cases, followed by low dairy intake, high processed meat intake, low vegetable and fruit intake, high red meat intake and high intake of sugar-sweetened beverages;
• The largest number of cancer cases associated with poor diet was for colorectal cancer (52,225). That was followed by cancer of the mouth, pharynx and larynx (14,421), uterine cancer (3,165), breast cancer (post-menopausal) (3,059), kidney cancer (2,017), stomach cancer (1,564) and liver cancer (1,000);
• Of the diet-associated cancer cases, approximately 16 percent were attributable to obesity-mediated pathways.
• Middle-aged men (45-64 years) and some racial/ethnic groups (non-Hispanic blacks, Hispanics and others) had the highest proportion of diet-associated cancer burden compared to other age, gender, or racial/ethnic groups.

The researchers investigated cancer-associated dietary habits using data from two National Health and Nutrition Examination Survey cycles (2013-2014 and 2015-2016). The team linked consumption data with cancer incidences in 2015 recorded by the Centers for Disease Control and Prevention's National Program for Cancer Registries and the National Cancer Institute's Surveillance, Epidemiology and End Results program.

Optimal dietary intake was outlined based on assessments by the World Health Organization's Global Burden of Disease (GBD) project. The researchers modified the GBD comparative risk assessment framework's population-attributable fraction (PAF) equation to estimate the proportion of all cancer cases that can be attributed to the suboptimal diet in each age, gender and race/ethnicity stratum.

The researchers caution that self-reported dietary intake data is subject to measurement error. In addition, diet-cancer risk estimates may differ by sex, age, race/ethnicity and other modifiers. Therefore, it was not possible to account for how the dietary factors might interact with each other when consumed together.

This study is a part of the Food Policy Review and Intervention Cost-Effectiveness (Food-PRICE) research initiative, a National Institutes of Health-funded collaboration led by researchers at the Friedman School. It works to identify cost-effective nutrition strategies to improve population health in the US.

In recent years, dietary factors have been closely evaluated for their potential in either preventing or inducing cancer. UK Cancer Research notes that obesity causes more than 60 cases of cancer a day, making it the second biggest cause of cancer in the UK after smoking. And new research in probiotic treatment has unveiled the innate linkage between gut health and cancer, which can be shifted by a person’s dietary choices.

By Benjamin Ferrer